Tire sensor modules or transponders, which are arranged, for example, in the interior of a tire, are known for the purpose of monitoring tire states, in particular a tire pressure, of tires of a commercial vehicle. Such tire sensor modules are designed to capture a tire pressure, mechanical stress states in the tire and a tire temperature on the basis of a fixed position, to process them and to transmit them by radio-frequency (RF) radio signal to an electronic control unit (ECU) of a monitoring system using a data message. The control unit receives the data message via a receiving module of the monitoring system and, on the basis of limit values, outputs a status signal to the driver, for example if it has been established that there is a tire pressure below a limit value at one of the tires. DE 102 43 441 A1 discloses an example of such a tire sensor module. Furthermore, a tire sensor module can use the data message to transmit a tire sensor module state to the control unit, for example a sensor fault or the presence of a loose tire sensor module, and said tire sensor module state can be output to the driver using the status signal.
When the tires of a two-part commercial vehicle or commercial-vehicle/trailer combination comprising a towing vehicle and a trailer vehicle, that is to say a semi-trailer or trailer, are monitored, the tire sensor modules of the towing vehicle are already stored in advance in the control unit by means of a sensor identifier or a sensor identification, the respective tire sensor module being uniquely associated with a tire of the towing vehicle. When a trailer vehicle is connected to the towing vehicle for a relatively long period, the tire sensor modules of this trailer vehicle can likewise be stored in the control unit and uniquely associated with the individual tires. However, when the trailer vehicle is frequently changed, the tire sensor modules of the trailer vehicle are incorporated by the monitoring system by means of automatic trailer detection. As a result, in the event of the trailer vehicle being changed, there is no need for manual storage, but the respective tire sensor modules of the tires of the trailer vehicle cannot be associated with a particular tire on the basis of a fixed position.
For automatic trailer detection, the monitoring system in a moving commercial vehicle monitors a monitoring region for data messages from arbitrary tire sensor modules that are not yet known to the control unit. If a new or unknown tire sensor module is detected, it is established, and the plausibility thereof is checked, over a relatively long period of up to 30 minutes for example, whether or not the unknown tire sensor module belongs to the driver's own trailer vehicle. This is carried out, for example, by checking whether or not the tire sensor module moves concomitantly with the towing vehicle over this period by monitoring whether a particular number of data messages are transmitted by this unknown tire sensor module over this period. Once the trailer detection has concluded, i.e. affiliation of the tire sensor module or else of multiple tire sensor modules to the driver's own trailer vehicle has been established, the monitoring system is ready to also process and evaluate the corresponding data messages of the tire sensor module and to output status signals, for example, on the basis of the captured tire states and/or tire sensor module states.
A disadvantage in this case is that the tire states and/or tire sensor module states cannot be output on the basis of a fixed position, since, after conclusion of the trailer detection, the control unit does not know at which tire the tire sensor modules are arranged. Since the number of wheels is also unknown, it is also not possible to establish whether data messages are also actually received from every tire of the vehicle or possibly one of the tire sensor modules is faulty and no longer transmits data messages. In addition, the incorporation of all tire sensor modules detected in the monitoring region and associated with the driver's own trailer vehicle takes a very long time and, until the trailer identification is complete, the driver of the commercial vehicle is provided with no acknowledgement about the state of the tires of his trailer or about the state of the tire sensor module, for example in the event of a faulty sensor.